Conventionally, there are game machines such as slot machines or pinball machines that are provided with a decoration device that shows a pattern such as a logo mark or characters depicted on a display panel to gamers by spreading the light from a light source over a wide range with a light guide plate and using that light to illuminate the display panel on which the pattern is depicted (e.g., see JP 2011-244930).
With the decoration device disclosed in JP 2011-244930, switching the pattern that is displayed was not envisaged. On the other hand, being able to switch the pattern that is displayed according to the state of the game is preferable in order to enhance the gamer's enjoyment. Meanwhile, an illumination device that has a tabularly formed light guide plate having light transmittance and that causes a pattern that depends on the incident direction of light on the light guide plate to be displayed has been proposed (e.g., see JP 2003-519810).
For example, the illumination device disclosed in JP 2003-519810 has a panel made from a light transmissive material, and the panel has a light exit window, a back wall opposing the light exit window, and light transmissive first and second end surfaces that are arranged between the light exit window and the back wall in different positions to each other. A first optical symbol formed on the back wall is displayed as a result of light that enters the panel from a light source opposing the first end surface being reflected by a plurality of triangular prisms arranged side-by-side on the first optical symbol and exiting from a light exit surface. On the other hand, a second optical symbol formed on the back wall is displayed as a result of light that enters the panel from a light source opposing the second end surface being reflected by a plurality of triangular prisms arranged side-by-side on the second optical symbol and exiting from the light exit surface. JP 2011-244930 and JP 2003-519810 are examples of background art.